[R-meta] forest plot and study-specific effect

[Viechtbauer, Wolfgang (NP)]

Dear Yefeng,

Plotting the BLUPs has been done before. See Figure 3 in:

van Houwelingen, H. C., Arends, L. R., & Stijnen, T. (2002). Advanced methods in meta-analysis: Multivariate approach and meta-regression. Statistics in Medicine, 21(4), 589-624.

Actually, the forest plot shows the individual estimates, plus the BLUPs.

You can find a recreation of this here:

https://www.metafor-project.org/doku.php/analyses:vanhouwelingen2002

I think there are various reasons why the default is not to show the BLUPs. For example, the estimates are simply what was found in each of the invididual studies, while the BLUPs depend on what other studies are included in the analysis and the values also depend on the specifics of the modeling approach used. But showing both (as above) is definitely interesting.

Best,
Wolfgang

> -----Original Message-----
> From: R-sig-meta-analysis <r-sig-meta-analysis-bounces using r-project.org> On Behalf
> Of Yefeng Yang via R-sig-meta-analysis
> Sent: Wednesday, June 5, 2024 08:14
> To: r-sig-meta-analysis using r-project.org
> Cc: Yefeng Yang <yefeng.yang1 using unsw.edu.au>
> Subject: [R-meta] forest plot and study-specific effect
>
> Dear community,
>
> I have a small question about the forest plot used in the meta-analysis.
>
> The forest plots and their varieties are often used in meta-analysis papers to
> show the overall/grand mean, individual effect size estimates, and other
> relevant info depending on the software making them. We know the effect size
> estimates from individual studies are usually noisy or not very precise. But,
> why do meta-analysts prefer to report individual effect size estimates rather
> than the study-specific effects (which benefit from the shrinkage or borrowing
> of strength). Or, put differently, the developers of software that can make
> forest plots do not seem to provide the option of showing study-specific effects
> (I did not check carefully; some software or packages might provide this
> functionality). Is there any specific reason? Or, it is just a convention.
>
> Best,
> Yefeng